Dual-mode switching of diffraction efficiencies. using either light or an electric field, is possible with a diffraction grating prepared from an;azobenzene-polymer-stabilized liquid crystal. Light-induced switching resulted from the cis-trans photoisomerization of the azobenzene unit, resulting in the nematic-to-isotropic phase transition of the liquid crystal (dark fringes in the Figure). This switching behavior is reversible and repeatable for many cycles.